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MA: Fachverband Magnetismus
MA 30: Skyrmions II
MA 30.4: Vortrag
Mittwoch, 20. März 2024, 16:00–16:15, EB 301
Chemical potential of magnetic skyrmion quasiparticles in heavy metal/iron bilayers — •Balázs Nagyfalusi1, László Udvardi1, László Szunyogh1,2, and Levente Rózsa3,1 — 1Budapest University of Technology and Economics, Budapest Hungary — 2HUN-REN-BME Condensed Matter Research Group, Budapest, Hungary — 3HUN-REN Wigner Research Center for Physics, Budapest, Hungary
We performed metadynamics Monte Carlo simulations to obtain the free energy as a function of the topological charge in the skyrmion-hosting magnetic model systems (Pt0.95Ir0.05)/Fe/Pd(111) and Pd/Fe/Ir(111), using a spin model containing parameters based on ab initio calculations. Using the topological charge as collective variable, this method allows for evaluating the temperature dependence of the number of skyrmionic quasiparticles. In addition, from the free-energy cost of increasing and decreasing the topological charge of the system we determined chemical potentials as a function of the temperature. At lower temperature, the chemical potential for creating skyrmions and antiskyrmions from the topologically trivial state is different. This splitting of the chemical potential is particularly pronounced for large external magnetic fields when the system is in a field-polarized phase. We observed a change in the shape of the free-energy curves when skyrmion-skyrmion interactions become more pronounced.
Keywords: skyrmions; chemical potential; theory; ab initio; metadynamics